1. Field of the Invention
The present invention relates to a wiring board and its manufacturing method, in particular, to a wiring board having a high-density wiring region, and to a method for manufacturing such a wiring board.
2. Description of Background Art
As IC chips are becoming finer and more highly integrated, the number of pads formed on the uppermost layer of a package substrate is on the increase. In accordance with such an increase in the number of pads, the pitches of those pads are also becoming finer. To respond to such fine-pitch pads, wiring pitches of package substrates are also rapidly narrowing (for example, see International Patent Publication WO/2007/129545).
Such a wiring board has a high-density wiring region inside. Specifically, an electronic component, in which a high-density wiring layer is formed on a substrate made of a heat-tolerant base material such as silicon or glass with a low thermal expansion coefficient, is incorporated in interlayer insulation layers of a wiring board. The entire contents of this publication are incorporated herein by reference.